Examples are always the best things for clarifying a concept due to the exemplification that follows.
Let us suppose, then, that I am a civil engineer who has to build a building...
During the project, my son asks me to join him; so, enthusiastic about his curiosity regarding my work, I explain all the phases to him, from the design to site management: - here we have to do a pour with so much cement, here the beams must be x wide with a square base and y high, the screed on the floor must be made of expanded clay so as not to weigh down the floor too much, the first team of workers will do this, the second that, on the second day we send the electricians and plumbers etc. etc. -
We go to the construction site and begin managing the workers. He follows along and takes note of everything I have told him.
Well... My son at 12 years old will potentially be able to do the exact same building in another place and will be able to manage the workers by imposing the same directives that I imposed on the building I have already constructed.
Let us suppose that my son was so good at copying my work on the first building that he earned the first pages in the newspapers: "12-year-old child designs and builds small apartment building".
They therefore ask him to build a different, larger building... The moral of the story -> He doesn't know how to do it, and if he did, the building would probably collapse as soon as they reached the second floor... It would collapse because he is not a real engineer; he is just a child who has copied his father's directives. He cannot know how to do the cement calculations, he wouldn't know how to distribute the weights of the floors, he wouldn't know how to calculate tolerances. He is just a child who has copied word-for-word what his father did.
Now... Probably the method of copying his father could bring some benefits in the future by making him passionate about the subject and then pursuing the path of civil engineering when he is grown and capable of understanding the engineering at the base of constructions, but it could also lose interest once he discovers that the path to becoming an engineer is not just managing workers and drawing projects, because he would understand that before drawing projects and managing teams of workers, there are many calculations to be made (he would discover a part that might be boring for him).
With this I mean that things should be done in stages. One must provide the foundations of construction by introducing materials, talking about the physical bases of load and load tolerance etc. etc. These are tools that a student can then use in different contexts so that if tomorrow someone were to ask to build a building different from the one his father built, he could answer: - No problem -.
In the piano, the basic setting of pianistic technique, solfeggio, and music theory are topics too important to be glossed over and require the right time—or rather, the time they deserve—to be assimilated, especially if taught to children. Sitting at the piano and showing them for a year straight which notes to play is a shortcut that, in my very modest opinion, leads nowhere, or at least serves little if not nothing. At this point you might reply saying: "But you yourself have often said that technique should be assimilated into music and not just through technical exercises and finger gymnastics". "Yes," I reply, "technique must be assimilated in a musical context that is however within the reach of the boy/child, so that it can be understood and experienced in other musical contexts."
One must accept the fact that to achieve certain results, one must also do the dirty work, in stages, with much dedication and sacrifice, because one does not become a pianist by copying others, just as one does not become an engineer by copying others. This thought I have just mentioned reminds me very much of a phrase by Carlo Rubbia interviewed on Ballarò when speaking of his perplexities regarding cold fusion, where he said (non-verbatim quote because I don't remember exactly, but this was the sense): - I don't believe God has given us a gift from which to derive energy in such a simple way -.
Turning back to the piano, I am ready to bet 10 to 1 that if after those beautiful virtuoso videos of mature Liszt, we put before those children, on the music stand, a piece taken at random from the Cesi-Marciano, they would not be able to play a single bar in a row.
At this point (rhetorical question) "a question spontaneously arises to me"... What have these children learned?
Answer: - a single piece in an entire year of study with the sole purpose of putting on a show and putting their teacher and his "revolutionary" technique under the spotlight -.
PS. Obviously, I reiterate, this is just my very humble opinion.